Current methods of minimally invasive spinal fusion primarily focus on the interbody space and use of an interbody spinal implant with bone grafting inside the intervertebral disc space. Traditionally, surgeons have performed an open procedure for spinal fusion that involves both the interbody fusion and a posterior lateral fusion. The posterior lateral fusion had been performed an open manner with tissue retraction and direct visualization of the posterior elements including the midline elements of the facet and pars intra-articularis, as well as the more lateral elements of the intertransverse process. With the advent of minimally invasive spinal fusion, direct access and visualization of the midline and lateral elements of the vertebral bodies have been difficult to perform in a minimally invasive manner, while access to the disc has been done with tubular retractors dilating tissues and muscle layers.
A number of investigators have proposed using tubular access to the posterior elements for percutaneous delivery of graft material. However the anchor points for these tubular elements have generally been of a fixed nature and do not allow for the multiaxial motion of the delivery system needed for broad access and visualization of the midline and lateral bony elements. For example, Oktavec et al. in U.S. Patent Application Publication No. 2012/0253316, entitled “Percutaneous Biologic Delivery System”, filed Mar. 28, 2012, disclose such a fixed anchor point where the pivot points are distal from the fixed pin based anchor point and therefore have limited mobility. In addition, the pivoting element is relatively distant from the anchor element, which will tend to result in a more significant retraction of the surrounding tissues and muscle.
Accordingly, there is a need for an improved minimally invasive spinal fusion procedure that will provide for more efficient and desired preparation of the surrounding bony surfaces prior to delivery of an implant and bone graft materials.